Author

Date of Award

Degree Name

Department

Educational Leadership, Research and Technology

First Advisor

Dr. Brooks Applegate

Second Advisor

Dr. Timothy Michael

Third Advisor

Dr. Christopher Cheatham

Fourth Advisor

Dr. Jesaaca Spybrook

Abstract

Ultrasound is a thermal modality that utilizes acoustic energy to promote heating. While there are many factors that affect heating of body tissues, the effects of skinfold thickness and skin temperature upon ultrasound heating have not been studied extensively. In addition, while temperature typically follows a linear trend, past research typically uses ANOVA or regression analysis to examine this relationship; but these models examine the within-subject effects (time) and between effects (usually groups) at the group level, not the individual level. Therefore, the purposes of this study are to determine if skin temperature and skinfold thickness are predictors for intramuscular tissue temperature changes during an ultrasound treatment and to examine different statistical models for this data. Thirty-two subjects had an absolute intramuscular depth measured at 1.5 cm from the surface of the calf and relative intramuscular depth at one-half the skinfold thickness added to the absolute depth. Two temperature probes were inserted at the respective depths and a surface temperature wire was affixed to the middle one-third of the treatment area. An ultrasound treatment consisting of 1.0 W/cm2 using a 3 MHz frequency was applied until the absolute temperature reached 3° above baseline temperature. Data were analyzed with ordinary least squares regression, hierarchical linear modeling (HLM), and mixed methods repeated measures (MMRM) techniques. Based upon the different trends within the data, it was concluded that HLM, because of examining the within-person effects and parsing out the error components, was a better fit model for analysis. HLM showed that skin temperature was a significant predictor for absolute and relative intramuscular temperatures, while regression MMRM showed skin temperature to be predictive for relative temperature. HLM also showed skinfold thickness to be predictive of relative temperature. Total heating rates for absolute and relative intramuscular depths were 0.61°C and 0.42°C per minute, respectively. In conclusion, it appears that tissue temperatures at the relative intramuscular depth (greater than 1.5 cm) can be better predicted using skin temperature and skinfold thickness and that HLM, examining the within-subject temperature variability during the ultrasound treatment, was the appropriate model.